Fuel octane.. 91,95 & 98

[xpaladoshous]

Hello all. Just wanted to get your thoughts on suitable fuel for my outboard. I have a 99 model 150hp Johnson 2 stroke. I have always used 95 in it but was told recently that that era of outboard should only be run on 91.. due to the 95 octane burning a bit hotter??

Any thoughts??

I would never use the e10 and i thought the 95 would be a little cleaner burning than the 91?? Would it make much differance to performance or engine life?

[scottar]

I have never run any of my outboards, even my E-tec , on anything other than 91 and have never had a fuel related issue (touch wood). IMO it is far more important to purchase your fuel from a known reputable supplier, maintain your fuel system (breathers clear, oring seals on fillers etc), have a good quality water separating filter and as you have indicated never use ethanol based fuel.

[Chimo]

And pour your ULP 91 fuel into your tank through a water collecting, dirt catching system like a "mr Funnel" unit. No I don't get a cut but have an old metal tractor diesel fuel one I have been using for the last thirty years on both ULP and diesel!

There is a recent good thread on here that illustrates why having two motors and two tanks won't save you if you fill them both from the same servo that includes water and other crap at no extra charge. http://www.ausfish.com.au/vforum/showthread.php/201935-Broke-down-AGAIN?highlight=funnel

Cheers
Chimo

[The Black Unicorn]

And pour your ULP 91 fuel into your tank through a water collecting, dirt catching system like a "mr Funnel" unit. No I don't get a cut but have an old metal tractor diesel fuel one I have been using for the last thirty years on both ULP and diesel!

There is a recent good thread on here that illustrates why having two motors and two tanks won't save you if you fill them both from the same servo that includes water and other crap at no extra charge. http://www.ausfish.com.au/vforum/showthread.php/201935-Broke-down-AGAIN?highlight=funnel

Cheers
Chimo

how do they go with auto cut off of bowser? Do they tend to overflow?

[Chimo]

how do they go with auto cut off of bowser? Do they tend to overflow?

Same as any boat tank I guess; you can hear when they are getting full and if I fill too fast my breathers gurgle and spurt as the tank is getting close to full.
I just don't go flat out but rather put the fuel in slower to avoid the overflow problem.

[Fed]

Do you ever catch anything Chimo?

[Chimo]

No Fed, I'm very careful!

[TheRealAndy]

Use the octane rating specified by the manufacturer. Who ever told you that a higher octane rating runs hotter is speaking nonsense. Octane rating is a measure of the fuels resistance to detonation, nothing more. Unless your engine runs hot, or runs at a higher compression then there is no advantage to using higher octane fuels. However, using higher octane fuels will not damage your engine..

For those who try and measure performance by octane rating, you will be disappointed to know that when lower octane fuel stocks are running low at the refinery, and the higher octane fuel stocks are running high, you local servo might be dishing up 98 from the 91 fuel bowser. The octane rating on the pump is the minimum, and it may actually be higher.

[docaster]

What about the theory of adding half a tank of 98 to 12month old fuel